1. Field of the Invention
This invention relates in general to processes and apparatuses for removing contaminants, and more particularly, to those processes and apparatuses for removing contaminants from substrates using supercritical fluids
2. Description of the Related Art
Miniaturization of microelectronic circuits allows more circuitry to be incorporated within an individual integrated circuit. The increased density is possible due to the reduction in size of geometries of components within those integrated circuits. Other microscopic components, such as a micro-mechanical electrical switch (MEMS), micro-optical switches, and the like, are also being reduced in size. However, the reduction in size is not without its problems.
FIG. 1 includes a prior art illustration of a cross-sectional view of a portion of a semiconductor device substrate 100. The semiconductor device substrate 100 includes an interconnect layer 110, a second interconnect level 120, a third interconnect level 130, an insulating layer 142, and a patterned resist layer 146. The second interconnect level 120 includes a patterned insulating layer 122 and a dual inlaid interconnect 124, and the third interconnect level 130 includes a patterned insulating layer 132 and a dual inlaid interconnect 134. Each of the insulating layers 122, 132, and 142 may include one or more insulating films. Likewise, each of the interconnects 124 and 134 may include more than one film.
Although not shown, the interconnect layer 142 is significantly thicker in portions not shown in FIG. 1. Prior to forming the patterned resist layer 146, the insulating layer 142 has been patterned a first-time to form interconnect trenches within the insulating layer 142. When forming the resist layer 146 over the patterned insulating layer 142, the thickness of the resist layer 146 can be relatively thick within the trenches previously formed, such as that shown in FIG. 1. The thickness of the patterned resist layer 146 within that trench can exceed more than approximately two microns.
An opening 148 is defined by the patterned resist layer 146 and may be formed using conventional photolithographic techniques. The opening 148 may have a dimension of approximately 0.4 microns and would generally correspond to a minimum geometry for a via portion of a dual-inlaid interconnect. The aspect ratio of the opening 148 may exceed 5:1. When developing and rinsing the resist layer 146, contaminants 150 (e.g., water) may remain near the bottom of the opening 148. Removing the contaminants 150 generally is very difficult as many organic solvents (e.g., ketones) that could remove the contaminants 150 may erode or dissolve the patterned resist layer 146, thereby, distorting the image patterned. The contaminants 150 need to be removed without significantly changing the shape of the patterned resist layer 146 or otherwise significantly adversely affecting the underlying portions of the substrate.
In one attempt to remove a contaminant from a substrate, a dense phase gas can be used to help remove contaminants from a substrate. For example, a dense phase gas, such as carbon dioxide (CO2) may be used to remove photoresist from the substrate. In FIG. 1, the resist layer 146 is not to be removed or otherwise significantly altered in its shape. The attempt also addresses the desirability of adding water to the dense phase gas. In FIG. 1, water is to be removed from, and not added to, the substrate. Therefore, adding water to the dense phase gas may be counterproductive to removing water from the substrate.
An apparatus may be used with a supercritical fluid. The apparatus is configured to flow a fluid from a pressure vessel, through a cold trap, and then to a heat exchanger before reaching a pump. Such a configuration may not operate optimally because contaminants may not be removed very quickly because the fluid changes from a supercritical fluid to a liquid in the heat exchanger, which is downstream from the cold trap.